Bleaching and cleaning compositions have been extensively described in the art. It is also well known that it can be desirable to use peroxygen bleaches rather than chlorine bleaches for a variety of reasons. In particular, peroxygen bleaches are generally considered to be milder to fabrics than chlorine bleaches. However peroxygen bleaches have the drawback that they are generally less effective at lower temperatures. In response to this drawback, peroxygen bleaching compositions have been described which further comprise a bleach activator. A bleach activator reacts with a perhydroxyl ion to yield a peracid which is the "activated" bleaching specie.
But activated bleaching compositions have the drawback that the activator and the bleach tend to react in the composition in which they are formulated. Such compositions therefore tend to be chemically unstable.
A solution to this problem has been described in EP 598 170, where a hydrophobic bleach activator was formulated in a composition with a 35 hydrophilic bleach. The compositions in '170 were formulated as an emulsion comprising a hydrophilic phase and a hydrophobic phase. The hydrophilic phase comprised a hydrophilic nonionic surfactant and the bleach, while the hydrophobic phase comprised a hydrophobic nonionic surfactant and the hydrophobic liquid bleach activator.
These compositions are very satisfactory in terms of stability, however they impose severe restrictions in terms of flexibility in formulation. For instance, it is difficult to incorporate significant amounts of anionic surfactants in these compositions, while it may be desirable to have some of them to perform better on whiteness and stain removal, in particular on particulate and enzymatic stains, particularly clay and blood. Also, the presence of a hydrophobic nonionic surfactant may be a drawback in certain conditions. For instance, at low temperature, high dilution, and in short wash cycles, hydrophobic nonionic surfactants provide limited contribution to the overall stain removal.
Thus it is an object of the present invention to formulate an activated bleaching composition which obviates the above issues.
It has now been found that such a composition can be formulated as a microemulsion of said hydrophobic liquid bleach activator in a matrix comprising water, and a hydrophilic surfactant system comprising an anionic and a nonionic surfactant.
In EP 598 170, the compositions are specifically mentioned to be emulsions only. Also, the presence of anionics is not recommended in '170. In EP 92 932, an activated bleaching composition is described which is in the form of an emulsion, and which requires an emulsifier for said bleach activator. In WO 93900847, activated liquid bleaching composition are described which comprise a hydrophobic liquid bleach activator, acetyl triethyl citrate (ATC). Liquid compositions comprising ATC are generally described in '847, which are not in the form of microemulsions.